This application is based on and claims priority to Japanese Patent Application No. 2000-236816, filed Aug. 4, 2000, the entire contents of which is hereby expressly incorporated by reference.
1. Field of the Invention
The present application generally relates to an engine control arrangement for controlling a watercraft, and more particularly relates to a method of controlling the operation and interaction of an engine and an overturn switch.
2. Description of the Related Art
Watercraft, including personal watercraft and jet boats, are often powered by at least one internal combustion engine having an output shaft arranged to drive one or more water propulsion devices. Occasionally, watercraft can overturn due to the sporting manner in which they can be ridden. Additionally, some watercraft operators purposely overturn the vehicles or submerge the vehicles during operation.
Watercraft use air ducts to supply air to a generally enclosed engine compartment. The air is drawn from within the engine compartment for combustion. Thus, when a watercraft overturns, there is a danger of water entering the engine compartment and entering into the engine itself through the induction system, which can cause extensive engine damage.
To reduce the likelihood of such engine damage, overturn switches have been used. The overturn switches generally detect watercraft movement that is consistent with a watercraft that is overturning. When such movement is detected, the overturn switch quickly outputs a signal that is used to shut-off the engine. By rapidly shutting of the engine, induction of water into the engine is much less likely during watercraft inversion.
Typical overturn switch designs generally are gravity-biased or centrifugal in nature. When the associated watercraft overturns, the switch""s position relative to gravity may cause the switch to detect the overturn or the rapid movement of the switch may cause the switch to detect the overturn. Unfortunately, watercraft are designed for sporting operation and often are operated in manners that cause rapid directional changes. For instance, the watercraft operator may engage in such activities as jumping, rapid turning and operation over rough water. Such activities can cause the typical overturn switches to falsely indicate an overturn leading to an undesirable and unnecessary engine shut off.
Watercraft also generally employ lanyard switches. Lanyard switches generally comprise a wrist tether (i.e., a wristband that is tethered to a xe2x80x9ckeyxe2x80x9d or other member that cooperates with a switch). When an operator of the watercraft falls from the watercraft, the wrist tether activates the lanyard switch and the engine is stopped. In effect, the lanyard switch generally operates as a kill switch that stops engine operation when the operator falls from the watercraft.
Over time it also is possible for the overturn switch 12 to experience certain failures due to normal aging and use of the watercraft 10. Generally speaking, the overturn switch 12 may experience two classes of failures: (1) the overturn switch itself or the wiring may become short-circuited, or (2) the connection to the overturn switch may become disconnected.
If an operator falls from a vehicle during operation of the vehicle in a planing speed range, the lanyard switch almost always will kill engine operation. Additionally, it has been discovered that most false positives from the watercraft overturn switches are encountered during operation at or above a watercraft planing speed (or an engine speed associated with planing, such as about 6000 rpm). The false positives can be irritating to the operator and can adversely affect water vehicle performance.
Thus, a method of reducing false overturn signals is desired. In addition, due to the relatively important role the overturn switch plays, a technique of monitoring the operability of the switch is desired.
Accordingly, an engine control arrangement is desired to properly control the interaction of an overturn switch and an engine in order to prevent unnecessary engine shut off In addition, the engine control arrangement preferably can be configured to warn the watercraft operator of a disconnected, shorted, or faulty overturn switch.
Thus, one aspect of the present invention involves a method of controlling engine operation in a watercraft. The method comprising sensing a engine speed, determining if said engine speed is above a preset engine speed associated with a watercraft planing mode, sensing an overturn signal from an overturn sensor, determining whether said overturn signal persists for longer than a predetermined period of time and stopping the engine when said overturn signal persists for longer than a predetermined period of time.
Another aspect of the present invention involves a personal watercraft comprising a hull. A substantially enclosed compartment is by the hull. An engine is disposed within the compartment and an overturn switch mounted within the compartment. The overturn switch communicates with an ECU through a switch circuit. The overturn switch has a first output, a second output and a third output, with the second output indicating a switch circuit malfunction to the ECU.